DHCP issues with unicast

[simon]

(2016-06-03 16:44)mcb30 Wrote:  This sounds like a bug in the network infrastructure. When the problem can be reproduced, how far does the DHCP response packet get before it gets dropped? (Does it get dropped, or does it just get sent to the wrong egress switch port?)

The DHCP is directly hooked up to our central H3C router. On the port where the agent should send out the relayed OFFER, we always see an ARP request for the IP address that was in the OFFER, which obviously doesn't get a reply. We see this ARP request in both cases, where the relayed packet appears on the wire (isc client) and where it does not appear on the wire (ipxe). That's pretty much how far we got. The next day it started working, and still does today.
Unfortunately I could not convince them to try to get logs or captures on the router itself, since the router is about a year old now, and the guy helping me out wasn't too familiar with its interface. So unfortunately no idea if the packet might have ended up on a wrong port. I was already glad he agreed to help me at all, since from the networking department's point of view, this is a corner case issue that doesn't impact anyone else anywhere.

Quote:I don't really want to add a mainline patch to work around what currently looks most likely to be a configuration problem specific to your infrastructure, unless the root cause is understood and it can be shown to be something that is likely to affect other people as well.

Understood. Was hoping a small on/off patch would be ok, but I see where you are coming from. We'll keep patching locally since we don't want to risk ending up giving the USB key to anyone having the same issues.

Oh and since the networking guy didn't want to blame it on a faulty config (I wonder why ) he considered the possibility of a firmware bug in the router, and started ranting about how Alcatel devices had the strangest bugs in the past and always required multiple updates...